Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-30-2010, 08:18 AM   #1
Veteran Member
WMBP's Avatar

Join Date: Dec 2006
Location: Dallas, Texas
Photos: Gallery
Posts: 2,496
min shutter speed in Av mode with flash

In his book The Hot Shoe Diaries, Joe McNally says that he keeps his camera in Av mode about 90% of the time, when using flash. He says he switches to M only when he's shooting in a space with very little ambient light; he switches to M in that case because in Av mode, the calculated shutter speed might be impractically slow (like 2 seconds or something). McNally is talking about what he does with this Nikon D3 and SB-800 and SB-900 speedlights.

Now, what I see working with a K20D and either Pentax AF-540 FGZ or Metz 58-AF flash units is different from what McNally sees. I'm hoping somebody can clear things up for me, either by pointing out what I'm missing or by confirming that the Pentax system simply works differently.
  • In Av mode, with no flash involved, the shutter speed will be calculated as slow as necessary to return a proper exposure. If setting the aperture to f/8 means that the shutter has to be 3 seconds, that's what the dial will return. I guess the camera assumes I'm using a tripod.
  • In Av mode, if there is a flash in the hot shoe, the camera WILL NOT return a shutter speed slower than 1/45th sec no matter how small the aperture is. Obviously the camera knows that there's a flash in the hot shoe and the camera has decided that 1/45th sec is as slow as the shutter should ever be when flash is involved.
  • In Av mode, the camera doesn't recognize a radio transmitter in the hot shoe as a flash, so it will calculate a very slow aperture just as if the hot shoe were empty.


What's with this 1/45th sec lower limit on the shutter, when flash is enabled? I've never noticed this before, because for a long time I've been using flash mainly in M mode. Now to be honest I would not mind having a lower limit on the shutter speed in Av mode—I just wish it were 1/30th sec instead of 1/45th sec. Is there a way to change this or is it hard-coded into the camera?

Apparently, to judge from what McNally says, things don't work this way on a Nikon D3.

Will

03-30-2010, 08:53 AM   #2
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
QuoteOriginally posted by WMBP Quote
In his book The Hot Shoe Diaries, Joe McNally says that he keeps his camera in Av mode about 90% of the time, when using flash. He says he switches to M only when he's shooting in a space with very little ambient light; he switches to M in that case because in Av mode, the calculated shutter speed might be impractically slow (like 2 seconds or something). McNally is talking about what he does with this Nikon D3 and SB-800 and SB-900 speedlights.

Now, what I see working with a K20D and either Pentax AF-540 FGZ or Metz 58-AF flash units is different from what McNally sees. I'm hoping somebody can clear things up for me, either by pointing out what I'm missing or by confirming that the Pentax system simply works differently.
  • In Av mode, with no flash involved, the shutter speed will be calculated as slow as necessary to return a proper exposure. If setting the aperture to f/8 means that the shutter has to be 3 seconds, that's what the dial will return. I guess the camera assumes I'm using a tripod.
  • In Av mode, if there is a flash in the hot shoe, the camera WILL NOT return a shutter speed slower than 1/45th sec no matter how small the aperture is. Obviously the camera knows that there's a flash in the hot shoe and the camera has decided that 1/45th sec is as slow as the shutter should ever be when flash is involved.
  • In Av mode, the camera doesn't recognize a radio transmitter in the hot shoe as a flash, so it will calculate a very slow aperture just as if the hot shoe were empty.


What's with this 1/45th sec lower limit on the shutter, when flash is enabled? I've never noticed this before, because for a long time I've been using flash mainly in M mode. Now to be honest I would not mind having a lower limit on the shutter speed in Av mode—I just wish it were 1/30th sec instead of 1/45th sec. Is there a way to change this or is it hard-coded into the camera?

Apparently, to judge from what McNally says, things don't work this way on a Nikon D3.

Will
will

checked *istD, K10D and K7D

*istD and K10D default to max sync in AV mode, i.e. 1/150 and 1/180 in leading curtain and 1/60 and 1/90 in trailing curtain sync for the 2 cameras respectively.

K7D allows for variable metering and shutter speed between 1/60 and 1/180 for leading curtain sync and 1/60 to 1/90 for trailing curtain sync.

I also did not notice this as I always shoot manual flash.

Maybe this is along the lines of alowing some partial fill flash when in AV mode without having to do really think about it.

Allowing shutters below 1/45 or 1/60 might be related to seeing motion blurr and ghosting with contributing natural light. That would be specifically why you would pick a lower speed and maybe the limit is just to avoid a problem for people wanting the camera to pop out good images regardless of how much thought they have applied to the process.

Last edited by Lowell Goudge; 03-30-2010 at 09:04 AM.
03-30-2010, 09:33 AM   #3
Site Supporter
enoeske's Avatar

Join Date: Jul 2009
Location: Surprise, Az
Photos: Gallery
Posts: 1,887
The camera is trying to intelligently balance the ambient light with the flash. You don't want a image with just light from the flash because it will look like people are in some black void. You don't want too little flash either, because you will need a long exposure and will surely introduce camera/subject movement. A good balance is 1/45s with flash to stop the motion but let some of the background and ambient light burn into the exposure.
03-30-2010, 09:38 AM   #4
Veteran Member
Jodokast96's Avatar

Join Date: Oct 2007
Location: Erial, NJ USA
Photos: Gallery | Albums
Posts: 2,133
I'm seeing different results with my K10D and both my 540 and 360 in Av.

Leading curtain gives me 1/30. Trailing curtain gives me the same shutter speed as no flash.

03-30-2010, 11:05 AM   #5
Veteran Member
WMBP's Avatar

Join Date: Dec 2006
Location: Dallas, Texas
Photos: Gallery
Posts: 2,496
Original Poster
Thanks for the informative replies so far, guys, and for helping me suss this out. Played with this a little more on my K20D. Here's what I understand now.

NOTE that the observations immediately below are based on working with the camera's built-in flash—not with a hot-shoe flash. Note also that the following observations all apply to shooting in Av mode (or effective-Av via the P/hyperprogram mode setting).
  • Using leading-curtain sync (what the K20d's display calls simply "Flash On"), the shutter speed will be limited to the range between 1/45th sec and 1/180th sec.
  • Using SLOW-SPEED SYNC, the shutter is limited at the high end to 1/180th sec, but at the low end, there doesn't appear to be a limit.
  • TRAILING CURTAIN SYNC is just like slow-speed sync, as far as the shutter is concerned: 1/180th sec limit at the fast end, and no limit at the slow end of the range. Of course, the flash is triggered now at the end of the exposure.

One thing I never really latched on to before is the difference between the normal "Flash On" (front-curtain, normal sync) setting and the slow-speed sync setting. I don't think I've ever used it. When I've used flash in P-TTL, I think I've generally left the camera in the "Flash On" setting and lived with it. But it looks as putting the camera into slow-speed sync causes the K20D to work the way Joe McNally's D3 works in Av mode by default. That's why he says he switches from Av into M mode sometimes: because in Av, the camera calculates too long a shutter speed.

The options in the Fn menu aren't very clearly named. (What a surprise!) It would have saved me some time if they were named as follows:
  • Leading curtain, normal speed sync
  • Leading curtain, slow speed sync
  • Trailing curtain, slow-speed sync

Apparently the camera doesn't support a trailing curtain normal-speed sync. Not sure why not.

*

Now, if I put the 540 FGZ into the hot shoe, in Av mode on the camera and P-TTL on the flash, the difference between normal sync and slow-speed sync that is controlled through the Fn button on the camera body STILL HAS AN EFFECT. In other words, if the camera's Fn screen is set to "Flash On", and the flash is set EITHER to front-curtain or trailing-curtain, the shutter speed is not going to be slower than 1/45th sec. But if the Fn setting is either of the slow-speed sync choices, then the shutter is permitted to go as slow as the camera thinks necessary.

NOTE that the 540 FGZ's dial still controls whether you get front-curtain or trailing-curtain action from the flash. So, if you want to allow a slower shutter speed than 1/45th sec, you can turn the camera's Fn setting to EITHER "Trailing Curtain Sync" (which is a slow-speed sync option) OR "Slow Speed Sync" (which is a leading curtain option).

Will
03-30-2010, 11:11 AM   #6
Veteran Member
Jodokast96's Avatar

Join Date: Oct 2007
Location: Erial, NJ USA
Photos: Gallery | Albums
Posts: 2,133
Something else to add. Was testing this with the 16-50. At 16mm, I get the results I posted above. However, at 50mm the shutter is set to 1/60 with leading curtain. Trailing curtain and no flash remain the same.
03-30-2010, 11:43 AM   #7
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
QuoteOriginally posted by WMBP Quote
Thanks for the informative replies so far, guys, and for helping me suss this out. Played with this a little more on my K20D. Here's what I understand now.

NOTE that the observations immediately below are based on working with the camera's built-in flash—not with a hot-shoe flash. Note also that the following observations all apply to shooting in Av mode (or effective-Av via the P/hyperprogram mode setting).
  • Using leading-curtain sync (what the K20d's display calls simply "Flash On"), the shutter speed will be limited to the range between 1/45th sec and 1/180th sec.
  • Using SLOW-SPEED SYNC, the shutter is limited at the high end to 1/180th sec, but at the low end, there doesn't appear to be a limit.
  • TRAILING CURTAIN SYNC is just like slow-speed sync, as far as the shutter is concerned: 1/180th sec limit at the fast end, and no limit at the slow end of the range. Of course, the flash is triggered now at the end of the exposure.

One thing I never really latched on to before is the difference between the normal "Flash On" (front-curtain, normal sync) setting and the slow-speed sync setting. I don't think I've ever used it. When I've used flash in P-TTL, I think I've generally left the camera in the "Flash On" setting and lived with it. But it looks as putting the camera into slow-speed sync causes the K20D to work the way Joe McNally's D3 works in Av mode by default. That's why he says he switches from Av into M mode sometimes: because in Av, the camera calculates too long a shutter speed.

The options in the Fn menu aren't very clearly named. (What a surprise!) It would have saved me some time if they were named as follows:
  • Leading curtain, normal speed sync
  • Leading curtain, slow speed sync
  • Trailing curtain, slow-speed sync

Apparently the camera doesn't support a trailing curtain normal-speed sync. Not sure why not.

*

Now, if I put the 540 FGZ into the hot shoe, in Av mode on the camera and P-TTL on the flash, the difference between normal sync and slow-speed sync that is controlled through the Fn button on the camera body STILL HAS AN EFFECT. In other words, if the camera's Fn screen is set to "Flash On", and the flash is set EITHER to front-curtain or trailing-curtain, the shutter speed is not going to be slower than 1/45th sec. But if the Fn setting is either of the slow-speed sync choices, then the shutter is permitted to go as slow as the camera thinks necessary.

NOTE that the 540 FGZ's dial still controls whether you get front-curtain or trailing-curtain action from the flash. So, if you want to allow a slower shutter speed than 1/45th sec, you can turn the camera's Fn setting to EITHER "Trailing Curtain Sync" (which is a slow-speed sync option) OR "Slow Speed Sync" (which is a leading curtain option).

Will
will


the plot sickens.

I went back after reading your post, and did some additional tests.

I had not looked at flash mode (low speed vs normal flash) and can cinfirm the K7 also functions as you note.

then I thought about the K10 and people posting that it wrks similarly, although mine did not.

In the ned I have found another variable. I had a KA mount lens on the K10D when I change that with a KAF mount lens, guess what, I now get variable shutter speeds in normal flash mode just like the K7.

I think there is another default, specifically if the camera can't read focal length it defaults to maximum shutter speed.

I have yet to confirm this on my *istD as well, since it has a screw mount adaptor installed and I am just too lazy to take it out.

so, in a nutshell,

probably (I have condfirmed this on my K7 but not the other 2 bodies I own yet)

all cameras have variable shutter speed in AV mode based on focal length read through the lens down to about 1 / (1.5 x focal lenght) I can only assume to avoid issues with shake and moving subjects

If no focal length is read, the flash sync speed is set to maximum, and does not change as a function of focal length entered at power if focal length is not known at the lens

Low speed sync seems to be disabled if focal length is not known

Low speed sync I suspect only goes down to shutter speeds within the metering EV range, You could test this by changing ISO and seeing if shutter speed lower limit changes also

this seems to apply for both internal and hot shoe flash. (verified on K7 for all but last point)
03-30-2010, 11:56 AM   #8
Veteran Member
WMBP's Avatar

Join Date: Dec 2006
Location: Dallas, Texas
Photos: Gallery
Posts: 2,496
Original Poster
why I'm thinking about all this

Let me explain why I'm trying to figure this stuff out. And to get to my explanation, I have to provide a little personal background.

Four years ago, when I started shooting weddings and other events and finally—for the first time in my life—tried to get somewhat serious about flash, I started out doing the safe and obvious thing, and I shot with P-TTL in P or Av mode. When I was NOT using flash, I was generally shooting in M.

Then I learned about dragging the shutter. In order to control BOTH aperture and shutter speed, that is, to slow the shutter speed down to 1/45th sec or 1/30th sec in order to bring in ambient light, I started shooting in M mode. Coincidentally and inconveniently, it was just about the same time that I discovered what hyperprogram mode does, and I started trying to use it when I wasn't using flash. So I went from M when not using flash & P when using flash, to P when not using flash & M when using flash. Yes, it was a bit confusing.

When I started using M mode for flash, I was still using P-TTL at first. Then I discovered the problem that P-TTL causes with fast blinkers. And that's when I started using the flash in manual mode as well.

In retrospect, the amazing thing is how well I was able to do. I'd set the camera (in M) to f/5.6 or something like that, ISO 200 or 400, shutter speed around 1/30th sec, take a test shot with the flash at 1/2 (my usual starting place), adjust the flash output, and then stick with it. Somehow, photos came out okay, most of the time. I'll have to be honest: I don't understand WHY this worked as well as it did. I think I intuitively tried to stay about the same distance from my subjects, and if I had to move back, I did adjust the flash output. But I also was bouncing a lot, so I really would expect that I'd have had MUCH more inconsistent results than I did.

*

So much for the background. Now, I'm trying to take my next step forward.

I've started using off-camera flash and wireless triggers more and more, when possible. There, I realize that I'm pretty much stuck with going full manual everywhere. That's fine. If I'm dealing with multiple flashes and radio triggers, I've probably got the time to think through my settings, take test shots and adjust, etc.

But when I'm shooting an event, with a single flash in the hot shoe, I'd like to get better results, better both in terms of image quality and in terms of consistency.

Which is one of the reasons I'm reading (well, rereading actually) Joe McNally's book. Now, McNally makes the point that he thinks it makes sense to take advantage of the camera's automated systems. He uses Av mode on the camera, and i-TTL on his Nikon flashes. I'm still a little unclear about whether he uses i-TTL when he's got a dozen Speedlights involved, triggered wirelessly. Is that even possible?

But I rather LIKE the idea of letting the camera do things for me, if it will really work. If I'm shooting an event, taking candids and shooting fast, I really would be delighted to use Av + P-TTL if I could make it work.

But I have two problems.

The first problem, is that Av mode won't let me drag the shutter quite the way I'd like. I get better results at 1/30th sec than at 1/45th sec. I've just figured out that I could put the camera into slow-speed sync, and then I can get a shutter speed slower than 1/45th sec. But the problem with THAT, as McNally himself acknowledges, is that sometimes the shutter speed will be a LOT slower. That means that, if I'm in Av using one of the slow-speed sync options, I can't really trust the shutter speed. Solution: Put camera into M mode.

The second problem is those fast blinkers. McNally actually acknowledges the problem of fast blinkers. Apparently he doesn't have it very often. His solution appears to be to use something found on the Nikon flash system, a flash lock button. You let the system calculate the right settings for a shot, then hit this button—and you have basically turned off the preflash. Which sounds a LOT to me like putting the flash into manual mode. In any case, I don't have a flash lock button. Solution: put flash into M mode.

Which leaves me precisely where I didn't want to be. :-)

*

Which is why I started this thread. I really desperately would like to make things as easy on myself as I can. I want to use as much of my very limited brain power as I can paying attention to things like composition and possibly how I'm going to bounce the flash, without having to worry constantly about either flash output or camera exposure settings. In other words, I'd really like to use Av + P-TTL. But it doesn't seem to make sense.

The other issue is, I'd like to understand how Joe McNally—who I recognize as somebody from whom I can learn a thing or two—manages to work the way he does. Maybe he's fibbing and he actually spends more time in M mode (on camera or on his Speedlights) than he admits.

Will

03-30-2010, 11:59 AM   #9
Veteran Member
WMBP's Avatar

Join Date: Dec 2006
Location: Dallas, Texas
Photos: Gallery
Posts: 2,496
Original Poster
Lowell,

"The plot sickens." Good one. I taught literature for twenty years and never heard that one. :-)

You've added a variable that I hadn't even thought of—the lens. (That is, you've added yet another variable I hadn't thought of.)

I was just now testing with K20D + Sigma 28 f/2.8 EX DC. I'll retry with a couple different Pentax lenses and see what I come up with.

Why oh why is this stuff so mysterious? Why couldn't somebody at Pentax have written a manual that just SAYS it all clearly?

Will
03-30-2010, 12:10 PM   #10
Veteran Member




Join Date: Sep 2007
Location: USA
Posts: 1,812
I don't have a K20D

But have you tried setting the flash to Slow-Speed Sync ?
It's supposed to work for both the on-board and external flashes.

Try that with Av and see if you get slower shutter speeds
(obviously in a dark enough environment to warrant a slower shutter speed)

From the K20D pdf manual:


EDIT to ADD

Sorry, I missed seeing you've already figured slow-sync.

What I do to avoid very slow shutter speeds is to use Slow-Speed Sync - but in Tv mode setting to something I can just handhold like 1/5th sec - then adjusting the ISO(or use AutoISO) to get enough exposure for the ambient light.

Last edited by UnknownVT; 03-30-2010 at 12:16 PM.
03-30-2010, 12:11 PM   #11
Veteran Member
Jodokast96's Avatar

Join Date: Oct 2007
Location: Erial, NJ USA
Photos: Gallery | Albums
Posts: 2,133
The problem is you sometimes get too slow of a shutter speed.
03-30-2010, 12:12 PM   #12
Veteran Member
WMBP's Avatar

Join Date: Dec 2006
Location: Dallas, Texas
Photos: Gallery
Posts: 2,496
Original Poster
QuoteOriginally posted by UnknownVT Quote
But have you tried setting the flash to Slow-Speed Sync ?
It's supposed to work for both the on-board and external flashes.

Try that with Av and see if you get slower shutter speeds
(obviously in a dark enough environment to warrant a slower shutter speed)

Vincent,

As I said in an earlier post, yes, I've tried slow-speed sync, and I describe the problem with it above. (I know that my posts are really long and I apologize.)

Will
03-30-2010, 12:20 PM   #13
Veteran Member




Join Date: Sep 2007
Location: USA
Posts: 1,812
QuoteOriginally posted by WMBP Quote
Vincent,

As I said in an earlier post, yes, I've tried slow-speed sync, and I describe the problem with it above. (I know that my posts are really long and I apologize.)
No it was me missing your find of Slow-Sync - but I have added an edit to tell you my way round - heck I'll just paste it here too:

"What I do to avoid very slow shutter speeds is to use Slow-Speed Sync - but in Tv mode setting to something I can just handhold like 1/5th sec - then adjusting the ISO (or use AutoISO) to get enough exposure for the ambient light."

I do this much more with my compact
some examples of slow-sync flash at slower shutter speeds -







all have EXIF re-attached (caveat PhotoBucket sometimes drops metadata).

Last edited by UnknownVT; 03-30-2010 at 12:25 PM.
03-30-2010, 12:28 PM   #14
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,312
QuoteOriginally posted by WMBP Quote
But I rather LIKE the idea of letting the camera do things for me,
Boy o boy talk about taking risks
QuoteOriginally posted by WMBP Quote
Lowell,

"The plot sickens." Good one. I taught literature for twenty years and never heard that one. :-)
I thought you'd like it

really, I was thinking about this a little, with what is discussed here, there is a good one page flash functionality description that should go somewhere. Ideally, with a little editing, we could scour the pentax forums and publish a book that was a real user's guide, written in common english (by all us common folk)
03-30-2010, 12:46 PM   #15
Veteran Member
WMBP's Avatar

Join Date: Dec 2006
Location: Dallas, Texas
Photos: Gallery
Posts: 2,496
Original Poster
QuoteOriginally posted by UnknownVT Quote
"What I do to avoid very slow shutter speeds is to use Slow-Speed Sync - but in Tv mode setting to something I can just handhold like 1/5th sec - then adjusting the ISO (or use AutoISO) to get enough exposure for the ambient light."
Hmmm. I've never thought about approaching it that way.

I just did a quick experiment. First I tried switching to Tv mode and setting the shutter speed to 1/30th sec. The problem there was that the aperture was recalculated as rather wider than I wanted. Shooting with flash, aperture still does have an effect on depth of field, which is why the "norm" for flash photography is Av mode rather than Tv mode.

Throwing Auto-ISO mode into the mix (in other words, shooting in Tv with Auto-ISO enabled and a range from 200-800), the aperture did stop down slightly, which was good, but I didn't think the image quality of the result was very good.

I could perhaps compromise on the shutter speed issue and accept 1/45th sec as a minimum, but I'm pretty sure that I HAVE to continue to be in control of the aperture. So Tv mode, with or without auto-ISO is a non-starter for me.

*

Now, to sicken the plot further, let me add one more variable: I'm using rear-curtain sync on the flash. Why? Suffice it to say that McNally says that he shoots in rear-curtain sync exclusively, all the time, and he has his reasons. And at the moment, I'm personally in "try to understand Joe McNally" mode.

Now this doesn't make a huge difference to the issues in this thread. I can still use rear-curtain either with P-TTL or Manual control of the flash, and with Av or M mode on the camera.

Will
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
aperture, av, camera, dslr, flash, mode, photography, return, sec, shoe, shutter
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
K-x Av mode shutter speed question macky112 Troubleshooting and Beginner Help 9 03-24-2010 10:13 AM
K-x: question about autopict mode slow shutter speed with flash manteiv Pentax DSLR Discussion 6 01-12-2010 12:39 PM
shutter speed in manual mode K200 Karen Troubleshooting and Beginner Help 1 02-20-2009 07:08 PM
AF-360FGZ on K20D Slow Shutter Speed in Av Mode Peter71 Pentax Camera and Field Accessories 3 09-11-2008 07:37 PM
Shutter speed too slow in Auto mode K200 PhotoGator Pentax DSLR Discussion 18 08-07-2008 05:35 PM



All times are GMT -7. The time now is 04:45 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top